Winterfront for motor vehicles



Oct 29, 1940- D. N. GATFIELD l WINTERFRONT FOR MOTOR VEHICLES Filed Aug.5, 1938 2 Sheets-Shea?. l

Oat. 29, 1940.-

D. N. vGATFIELD wINTERFRoNT Fox MOTOR VEHICLES Filed Aug.r 5. 193e 2Sheets-Sheet 2 @m lm i l www l .QN

Patented Oct. 29, 1940 UNITED STATES 'PATENT OFFICE 18 Claims.

My invention relates to shutters or winterfronts for radiatorsconstituting a part of a cooling system for internal combustion enginesemployed for automotive purposes.

In the operation of tractors, trucks, and the like, using distillate andkerosene fuels, it is customary to employ gasoline or the like volatilefuel for starting purposes, since distillate and kerosene fuels arequite heavy and require more heat for proper vaporization than isavailable under ordinary starting conditions, particularly duringperiods of cool cr cold weather. It is, therefore, highly desirable,when the engine is started, that it becomes heated quickly to the properworking temperature for use of the other and heavier fuel. It is alsohighly desirable that once the engine is brought to the proper heatedcondition and the heavier fuel cut in that the engine be maintained ator near a certain working temperature within a certain working range formost efflcient utilization of the fuel.

Heretofore, it has been proposed to aid the foregoing conditions by theuse of radiator shutters or winterfronts, but such prior devices havenot fully served the intended purpose and are objectionable for severalreasons. For example, it has been customary t-o employ winterfronts withoverlapping shutter blades which have been so constructed that, whenopen, they materially obstruct the free flow of air to the radiator,thereby causing the engine to become overheated. Also, it is customaryto employ a cooling fan behind the radiator for drawing air therethroughsupplementary to the air passing through the radiator by virtue ofmovement of the vehicle In the use of a fan, when the winterfrontshutters are closed, a suction is created by the fan which tends todistort the shutter blades somewhat along their overlapping edges,thereby breaking the seal A0 intended to be accomplished at that point,permitting cooling air to be drawn through the winterfront and radiatoreven when the winterfront is closed. Thislresults in delayed heating ofthe engine, with consequent inconvenience in use of the tractor or otherdevice, as well as increased fuel cost.

One of the objects of my invention is to provide a shutter orWinteriront for tractors, trucks,

and the like, by which all of the foregoing objectionable conditions arepractically eliminated. More particularly, it is the principal object ofmy invention to provide an adjustable winterfront having shutter bladesof such character that, when opened, they permit a free and practicallyunobstructed flow of air to the radiator, and

(Cl. 18S-62) which, when closed, are tightly sealed'against each otherat and adjacent their overlapping edges.

Another object is to provide a winterfront of the foregoing characterhaving shutter blades :f5 adapted to overlap in closed position, eachshutter blade being provided with a plurality of suction slots by whichthe suction of the fan is employed to cause the overlapping shutterblades to seal against each other at the point of overlap.

Additional objects are to provide an improved mounting for winterfrontshutter blades; and to provide a shutter or winterfront embodying theforegoing features which is of simple construction, is easy tomanufacture, and which is adapted 15 to perform'its intended functionsin a highly efficient rnanner. f

Other objects and advantages will become apparent as this descriptionprogresses and by referl 'ence to the drawings wherein- Figurel 1 is afragmental view of the front portion of a motor vehicle, such as atractor, embodying my invention, the several parts being illustratedsomewhat diagrammatically; `r

Fig. 2 is an enlarged rear elevationalor inside 'A25 view .of one formof shutter or winterfront embodying my invention, such as illustrated inFig. l;

Fig. 3 is an enlarged, fragmental front elevational view, partially insection, of the upper portion of the structure shown in Fig. 2, thestructure being shown in shutter-closed position;

Fig. 4 is a section taken substantially on line ll-4 of Fig 3;

Fig. 5 is a fragmental section similar to Fig. 3 except showing thestructure in shutter-open .35 position;

Fig. 6 is a section taken substantially on line 6 6 of Fig. 4;

Fig. 7 is a fragmental cross-sectional view of a modified form ofshutter structure that maybe 40 employed in carrying out my invention,the shutter blades being shown in closed position;

Fig. 8 is another fragmental sectional view of the shutter blades ofFig. 7, the same being shown in open position; v

Fig. 9 is a cross-sectional View of another form of shutter blade that Imay employ;

Fig. 10 is a fragmental, cross-sectional View of still another form ofshutter structure that may be used in carrying out my invention, thestructure being shown in full lines in closed position and in dottedlines in open position; and

Fig. l1 is` a fragmental plan view of one of the shutter blades shown inFig. 10.

Referring to Figs. 1 to 6, inclusive, a winterfront .55

20 embodying my invention is adapted to be mounted in front of aradiator 2| constituting a part of the cooling system for an internalcombustion engine 22. The cooling system may further include a fan 23 ofordinary construction driven from the engine 22 through a fan belt 23ain a conventional manner, The radiator 2| may take any suitable formarranged for the passage of air therethrough for the cooling of a liquidbeing circulated through the radiator. The engine 22 may take anydesired form but, for the purposes of this description, it will beunderstood that it is of a type for use in tractors, trucks, and thelike, and which is adapted for the use of distillate or kerosene fuels.It is to be understood, however, that, while my invention will bedescribed in its application to tractors, trucks, and the like,employing engines of the foregoing character, it is also well suited foruse with any other automotive vehicle employing an internal combustionengine using any suitable fuel.

The winterfront 2B is secured in front of the radiator 2| by anysuitable means including brackets 24 detachably connected at the sidethereof out of the path of the air passing through the winterfront 20and the radiator 2|. The' winterfront 20 takes the form of a detachableunit which includes a rectangularly shaped frame formed of a pluralityof strips 25. The frame strips 25 define an air passageway which isadapted to be opened and closed by a plurality of vertically disposedshutter blades 26. The frame strips 25 are of a Width slightly greaterthan the width of the shutter blades 26 so that the latter may bemounted within the frame and will be confined within the width limits ofthe frame in both the open land closed positions of such blades.

The shutter blades 25 are all of similar construction and only one willbe described in detail.

Each shutter blade takes the form of a flat and comparatively narrowstrip of sheet metal eX- tending substantially throughout the height ofthe winterfront. One longitudinal edge of each shutter blade 26 isturned over to provide a comparatively narrow right-angled flange 21thereat which strengthens the same suiiciently to prevent distortion ofthe shutter blade when it is moved about its pivotal support. Eachshutter blade 26 is pivotally supported at its opposite ends so that itmoves with a hinge-like movement about a vertical axis. Specifically, atthe opposite ends of the shutter blade, adjacent the side edge havingthe flange 21, I secure, by welding or otherwise, short swivel pins 28(Figs. 3, 4 and 5), the outer ends of which project slightly beyond theends of the shutter blade and rotatably engage in suitable openingsprovided in an internal frame-carried side member 29. A washer, or thelike, 30 is mounted upon each of the pins 28 between the frame part 29and the ends of the shutter blades so as to properly space the ends ofthe blades from the frame and to insure a free t and rotary bearingwhich will not tend to rattle and become noisy.

All of the shutter blades 26 are mounted in the manner above describedand they are interconnected through a common control means so that, uponactuation of the control means, they will all be moved simultaneouslyand to similar extent. More particularly, at the upper end of each ofthe shutter blades 26, I provide a right-angled arm 3| (Figs. 3 and 6),which arm may be formed integral with the shutter blade or may be aseparate strip welded thereto. Each of the arms 3| is connected by aswivel pin 32 to a laterally shiftable control bar 33 located within theupper part of the frame. 'I'he control bar 33 is provided with anupstanding pin 34 which projects out through an arcuate slot 35 formedin the top side member 25 of the winterfront frame; and it will be seenfrom the foregoing that by shifting the control bar 33 laterally all ofthe shutter blades 26 are moved to similar extents between open andclosed positions. This movement is accomplished by a link 36 (Figs. 2and 3), one end of which is connected to the pin 34 and its other end isswingably connected at 31 to one arm of a crank member 38 supported atone side of the winterfront frame by a swivel pin 39. The other arm ofthe crank 38 supports a block 40 swiveled therein and having ascrew-threaded opening 4| which receives the outer and threaded end 42aof a control rod 42. The other end of the control rod 42 is providedwith a handle 43 which is located conveniently tothe operator of thevehicle. By rotating the handle 43 in one direction, the outer threadedend of such rod is screwed into the block 40, swinging the crank 38rearwardly of the winterfront and, in turn, moving the link 36 to theright (as viewed in Fig. 2) thereby moving the control bar 33 to swingthe shutter blades 26 to an open position (Fig. 5). As the control rodhandle is moved in opposite direction, the operating parts are returnedto their normally closed position (Figs. 2 and 3) by a spring 44 mountedwithin the winterfront frame at the upper side thereof and having oneend engaged with a pin 45 carried by the control bar 33 and its otherend fastened to a frame-carried pin 4E. In the use of the foregoingarrangement the winterfront shutters 26 may be easily and quickly openedto any desired extent or closed, as operating conditions may require.

It is desirable, for reasons hereinabove stated, f

that the shutter blades be fully sealed against each other when closedto prevent the passage of air therethrough and through the radiator 2|to the engine 22. To this end, I construct and arrange the shutterblades 26 in such a Way that the suction established by the fan 23 isutilized to tightly seal the overlapped portions of the blades againsteach other. More particularly, the shutter blades are of such width andare so arranged that, when closed, the free edge portion of one blade isdisposed outwardly of and overlaps the flanged edge of the next adjacentshutter blade. Each shutter blade 26 (except the first one to the leftas viewed from the front in Fig. 3) is provided adjacent its flangededge 21 with a longitudinal row of spaced, comparatively narrow andelongated slots 41. By arranging the shutter blades 26 as abovedescribed, the slots in each blade are disposed inwardly of theoverlapping edge of the adjacent blade. In this way, each overlappingshutter blade is exposed to the suction of the fan 23 through the slots41 in each overlapped blade; and, when the shutter blades 26 are fullyclosed and the fan 23 is in operation, the suction created by the latteris effective through the slots 41 to draw the overlapping blade rounded,as best shown in Fig-6.

the right-angled: blade anges 2'1f` which are. of. slight'y height andoffer a minimum restriction to air iiow'.Y To furtherminimizezobstruction to air flow in the open position of thewinterfront, the free edges. of thev shutter blades are preferably Ifdesired, a

screenk 53 of sufiicient` size to cover the forward part of the.winterfront may be secured` to the frame members 25, asshown in Fig. 3l.

In some instances, dependent upon the length of' the shutter bladesandthe particular material employed', it may be desirable4 to furtherstrengthen the edge of the shutter blade that is connected' to the.frameA to prevent sagging, buckling or other distortion of the same; Inthat case, I may employl ashutter structure such as shown in Figs. 7 and8, wherein each of the shutterv blades 4S' has its swiveled or pivotededge rolled to provide a cl'osed tubular reinforcing bead 9'. Theshutter bladesY litoverlap each other, and that portion ofthe bead 49 ofeach blade which is overlapped is provided withv a longitudinal seri-esof spaced slotsv similar to the slots 41 (Figs. 2 and 3*) All oftheblades 48 are pivotally supported similarly to thev previouslydescribed blades 25 and their body portions are slightly offset at d8aso that the overlapping surfaces of the blades may seat flush againsteach other. Unless otherwise provided against, the

rolled or beaded blade edges 45 would tend to offer restriction to theflow of air through the winterfront when the shutter blades 58 areopened. To minimize such obstruction, theopposite sides of each bead i9rare provided withdiametrically opposed, longitudinally extending rowsof slots 5l which are disposed and aligned in aplane substantiallyparallel with the plane of the body of the shutter blades d8. In thisway, when the blades 48 are opened, as illustrated in Fig. 8, the

lo slots 5l are then disposed substantially parallel with the path ofair flow through thewinterfront so that air may pass through the slots5i with minimized restriction effect. W'henthe shutter blades 43 areclosed, the slots 5l also serve to connect the overlapped slots 5t withthe suction of the fan (such as the fan 23 of Fig. l). In other words,the suction of the fan is effective atv this time through the slots 5Gand 5l to seal the overlapping portions of the blades 5S against eachother as in the first-described form. Also, by locating the seal slots55 in the beads 49, narrower shutter blades may be employed with lesskblade overlap, thereby tending tol reduce the amount of blade materialrequired as well as the amount of space required for mounting andoperating the blades. It will be understood, however, that, if desired,the slots 5i may be located in the plane body portion of the' shutterblade closely adjacent to the bead i9 so that the suction of the fan is`directly effective through the slots to seal the shutter blades. Inother respects, the shutter structure just described is similar to andoperates like the structure previously described.

In some instances, I may employ a shutter blade like that shown in Fig.y9. This shutter blade, which is designated by the numeral 52, issimilar to that shown in Figs. 7 and 8 except that the bead 53 formed atthe pivoted or swiveled edge of the blade is not completely closed,thereby providing a co-ntiruous, open slot 5ft along the inner sidethereof. In this form, a longitudinal row of spaced slots 55 areprovided in the bead opposite the continuous slot 5ft thereby tending tofurther minimize restriction to air now through 75 the bead in the openposition lof the shutter blade.

Qtherwisetf thisblade is. mounted similarly to and operates like-theblade Structure of Fig.

In Figs'. 10i and l1 I have shown anotherform of.' shutterl wherein theshutter blades are so mountedthat the forward moving portion thereof isshortened, permitting the use of a frame of less depth while retainingthe sealing feature -of my invention. Specifically, in this form Iemploy shutter blades 56, each having at their opposite ends swivel orpivot pins 51 which are located at a point between the side edges of theshutter blade and somewhat closer to one edge thereof. These pivot pins51, which are similar to the pivot pins 28v of Figs. 3 to 5, inclusive,are preferably mounted' in the manner shown in Fig. 1l. is to say', ltheopposite end portions of the blades 56, at the appropriate position, areslitted at 58 thereby providing sections 59 that are alternately pressedoutwardly of the opposite faces of the blade 56, providing a circular,web-like, pin-receiving socket S0. Each pivot pin 51 may be secured inits respective socket in any desired manner. The end edges of the blades55 bounding the sockets 50 are recessed, as at 5 l, for reception ofthepin flange or Washer E2, as the casemay be, corresponding to the washer35 of the first-describedl form. I rhave found thaty good results may beobtained by mounting the pivot lpins inwardly of the so-called tail endof the blade at a point approximately one third of the width of theblade.- The blades 55', through their pivot pins 51, may be mounted andoperated in the same manner as the blades 2,6 of the i'lrst form, andthese blades, like the blades 48 of the form of Fig'. 7 and the bladek52 of Fig. 9, have their forward portions offset slightly outward sothat the blades will seat flush against each other in their closedposition.

The blades 56 are each further provided in their so-called tail endswith a longitudinal series of t suction slots 54, the arrangement beingsuch that the. tail end of each blade and the slots therein are.overlapped-by the forward offset portions of the overlapping blades. Inthis way, the suction of the fan, such as the fan 23 of Fig. 1, iseffective through the slots 641:0 :draw the end of the overlapping bladeinto close sealed relation with the tail end or overlapped surface ofthe adjacent blade and effect a seal as in the previously describedform. In this particular form, the suction action is quite positive and,with the suction acting on a substantial portion of the blade betweenthe pivoted portion thereof and the overlapped portions of the otherblade, the overlapped surfaces are clamped tightly together providinga..

very effective seal.

It will also be seen that by mounting the blade pivot intermediate itsedges the space required for movement of the same to and from an openposition, within the confines of a frame,'is reduced, thereby materiallyreducing the depth of the frame and providing a more compact structure.

I believe that the operation and advantages of my invention-will beapparent from the foregoing description. The winterfront is readilyadjustable between open and closed positions.

When it is closed, it is sealed in such a way that the full benefit ofheat developed in the prelimi- -nary operation ofthe engine maybeutilized to quickly bring the engine -to 'a desired heated condition.When the engine has become heated Vtor a desired working temperature andthe winterfront is opened, air'will pass through the latter,

under the control of the fan 23 and movement of Y That v the vehicle,with a minimum obstruction so that the full benefit of the coolingeffect thereof may be utilized for temperature control purposes. Theimproved manner of mounting the shutter blades reduces manufacturingcost, simplifies the structure as a whole, and aids generally in theaccomplishment of the advantages hereinabove stated.

I claim:

1. A winterfront or the like adapted for use with a radiator throughwhich air is drawn by a fan for cooling purposes, which comprises acasing adapted to be mounted in front of the radiator, a plurality ofshutter blades movable between an open and closed position and soarranged that they overlap each other in closed position, and aplurality of spaced slots in the overlapped portions of said bladesadapted to expose the overlapping surfaces of said blades directly tothe suction created by the fan for effecting a substantially sealedcontact between the surfaces of said blades which overlap each other.

2. A device of the character described which comprises a frame, aplurality of shutter blades, means for mounting said blades for swingmovement about one edge thereof, means by which all of said blades aresimultaneously moved to similar extents between an open and a closedposition, said blades being so constructed and arranged that theyoverlap each other in closed position, the overlapped portions of saidblades being provided with a longitudinally extending series of spacedslots through which the overlapping surfaces of said blades are exposed.

3. A device of the character described, which comprises a frame, aplurality of shutter blades each having one of its longitudinal edgesturned over to stiffen the same, means carried by said blades along thestilfened edge thereof at the opposite ends thereof only for swingablyconnecting said blades to said frame, means for moving all said bladesto similar extent between open and closed positions, said blades beingof such width and so arranged that the edge portion of one bladeopposite its stiffened edge overlaps the stiffened edge portion of theadjacent blade, and the overlapped of said blades each having alongitudinally extending series of slots adjacent its stiffened edge andthrough which the overlapping blade portions are rearwardly exposed.

4. A device of the character described comprising a frame, a pluralityof comparatively thin, plane-surface shutter blades disposed verticallyin said frame, each of said blades having one edge thereof turnedslightly out of the plane thereof to strengthen the same, swivel meansconnected yto each said blade at the opposite ends only thereof adjacentsaid strengthened edge and also swiveled to said frame for swingablymounting said blades for movement toward and `from a closed position,said blades being of such width and so located relatively that the freeedge of one blade overlaps the strengthened edge of the adjacent blade,and the overlapped portion of each blade having a plurality oflongitudinally extending spaced slots that are covered exteriorly by theoverlapping portions of adjacent blades in the closed position of saidblades.

5. A shutter blade for a device of the character described whichincludes an elongated planesurfaced body portion, a turned-over flangealong one side edge of said body portionv for stiffening purposes, ashort swivel member carried by said body portion at each end adjacentsaid turnedover flange, and said bodyportion being provided with alongitudinal series of slots located adjacent said turned-over flangebetween said swivel members.

6. A shutter blade for a device of the character described whichincludes an elongated planesurfaced body portion having one longitudinaledge rolled to provide a tubular strengthening bead thereat, swivelmounting means associated with said bead at the opposite ends only ofsaid body portion, and said bead having longitudinally spaced slotsextending substantially throughout the said body portion.

'7. A shutter blade for a device of the character described whichincludes an elongated planesurfaced body portion having one longitudinaledge rolled to provide a tubular strengthening bead thereat, swivelmounting means associated with said bead at the opposite ends only ofsaid body portion, said bead having a longitudinal series of slotsextending substantially throughout the length of said body portion, andsaid bead having additional and diametrically opposed, longitudinallyextending series of slots therein with each said additional seriesdisposed in a plane aligned substantially parallel with the plane ofsaid body portion.

8. A Winterfront or the like adapted for use with a radiator throughwhich cooling air is drawn by a fan, which comprises a frame adapted tobe mounted in front of the radiator, a plurality of plane-surface,comparatively narrow shutter blades mounted for swivel movement in saidframe, a rolled tubular bead formed along one edge of each said bladeand said blades being of such width and so located relatively thatsubstantially only the beaded edge of one blade is overlapped exteriorlyby a free edge of an adjacent blade in the closed position of saidblades, each of saidl blades in the beaded edge thereof havinglongitudinally spaced slots that are covered by the overlapping portionof the adjacent blade whereby the suction of the fan is effectivethrough said slots to seal the engaged overlapping surfaces of saidblades against each other in the' closed position thereof.

9. A winterfront or the like adapted for use with a radiator throughwhich cooling air is drawn by a fan, which comprises a frame adapted tobe mounted in front of the radiator, a plurality of plane-surfaceshutter blades mounted for swivel movement in said frame, a rolledtubular bead formed along one edge of each said blade and said bladesbeing of such width and so located relatively that the beaded edge ofone blade is overlapped exteriorly by a free edge of an adjacent bladein the closed position of said blades, each of said blades adjacent thebeaded edge thereof having separated longitudinal series of slots, someof which are covered by the overlapping portion of the adjacent bladeand others of which series are aligned and diametrically opposed anddisposed in a plane substantially parallel with the plane of said bladeswhereby air may pass therethrough in the open position of said blades,and said first-mentioned series of slots are connected to the suction ofthe fan in the closed position ofl said blades.

10. A shutter blade for a device of the character described, whichcomprises an elongated plane-surfaced body portion having one edgerolled to provide a tubular strengthening bead thereat, swivel mountingpins mounted in the opposite ends of said bead, said bead being soconstructed and arranged that there are a plurality of spaced slots oflongitudinally disposed and spaced slots in the side thereof disposedsubstantially in the plane of said body portion, and also openings insaid bead on opposite sides thereof and aligned with each other in aplane spaced from but substantially parallel with the plane of said bodyportion.

1l. A shutter blade for a device of the character described, whichcomprises an elongated plane-surfaced body portion having one edgerolled to provide a tubular strengthening bead ,thereat, swivel mountingpins mounted in the opposite ends of said bead, said bead being soconstructed and arranged that there are a plurality of spaced slots inone side thereof for permitting the passage of air through the bead atsubstantially right angles to the plane of said body portion, and aplurality of diametrically opposed openings in other sides of said beadand extending thereinto at substantially right angles to said slots andin a direction substantially parallel with the plane of said bodyportion.

12. A device of the character described which includes a plurality ofshutter blades, means secured to the opposite ends of each of. saidblades and at a point between the side edges thereof for mounting saidblades for swing movement between open and closed positions, said bladesbeing so arranged that the forward edge portion thereof on one side ofsaid mounting means overlaps the tail edge portion on the opposite sideof said mounting means of an adjacent blade, said overlapped tail edgeportions being provided With a longitudinal series of spaced slotsthrough which the overlapping surfaces of the forward blade portions arerearwardly exposed.

13. A device of the character described which includes a plurality-ofshutter blades, means secured to the opposite ends of each of saidblad-es and at a point approximately one third of the distance betweenthe side edges thereof for` mounting said blades for swing movementbetween open and closed positions, said mounting means dividing eachsaid blade into a forward and a tail portion,`said blades being soarranged that the forward portion thereof overlaps the tail portion ofan adjacent blade, said overlapped tail portions being provided with alongitudinal series surfaces of the forward blade portions arerearwardly exposed.

14. A shutter blade for a device of the character described, whichcomprisesan elongated body of rectangular outline shape, swivel mountingmeans carried by said body along one of the side edges thereof andprojecting from the opposite ends thereofsa1d body portion beingprovided overlapped by another through which Athe overlapping withlongitudinally spaced slots, the arrangement being such that when -theslotted b-lade body is blade the surface of the overlapping blade isexposed through said slots.

15. A winterfront adapted for use with a cooling system that includes afan that induces a flow of air by suction through the winterfront, whichcomprises a frame, a plurality of shutter blades movable between openand closed positions and so mounted that they overlap each other inclosed position, said blades having slots therein so arranged thatportions of the overlapping surfaces of said blades are directlyexpos-ed through the overlapped blade surfaces whereby the suction of afan located behind the winterfront effects a substantially sealedcontact between the blade surfaces when the blades are in closedposition.

16. A shutter blade for a device of the character described, whichincludes a flat body portion, a turned-over ange along one side edge ofsaid body portion for stiffening purposes, swivel means carried by saidbody portion and projecting therefrom at each end thereof adjacent saidflange, and said body portion being provided with longitudinally spacedslots so located that they will be covered by anoverlapping blade whentwo overlapping blades are brought into overlapping relation.

17. A shutter blade for a device of the character described, whichincludes a at body portion having one longitudinal edge rolled toprovide a tubular strengthening bead thereat, swivel ymeans associatedwith said bead and extending from the opposite ends of said bodyportion, said bead having at least three series of spaced slots therein,two of which series extend oppositely to each other in a planesubstantially parallel with the plane of said body portion.

18. A device of the character described comprising a frame, a pluralityof shutter blades disposed vertically in said frame, each of said bladeshaving one edge thereof turned slightly out of the plane thereof tostrengthen the same, swivel means `connected to each blade andAextending from the opposite ends thereof adjacent said strengthenededge, said swivel means being mounted in said frame for swingablymounting said blades and for movement toward and from a closed position,said blades being of such Width and so located that the free edge of oneblade overlaps the strengthened edge of the adjacent blade, and theportion of each blade adapted to be overlapped by an adjacent bladebeing slotted to expose a part of the engaging surface of theoverlapping blade.

D. NORVELL GATFIELD.

